At the base of the Cambrian rocks in Wales, Dr. Hicks has described a marked volcanic series under the name of "Pebidian," which he claims as pre-Cambrian, alleging that it is separated from the Cambrian system by an unconformability, and a band of conglomerates. I have carefully studied the evidence on this ground, and have come to the conclusion that there is no unconformability at the line in question, but that the ordinary Cambrian strata graduate downwards into the volcanic group and can not be disjoined from it. I therefore regard the so-called "Pebidian" as merely marking the duration of a volcanic period in early Cambrian time. It will thus be seen that according to my view the unmistakably pre-Cambrian rocks of Britain consist of, first and oldest, the Lewisian gneiss; second, the Torridonian sandstones and conglomerates. The Uriconian and Longmyndian formations may prove to be in part or in whole equivalents of the Torridonian. The Dalradian rocks have not yet had their position determined. They may possibly mark a distinct pre-Cambrian series, but it seems quite as probable that they are only a metamorphic complex in which Archæan, Torridonian and Cambrian, or even Lower Silurian rocks are included. =Sir Archibald Geikie=, Director-General of the Geological Survey of Great Britain and Ireland. ARE THERE TRACES OF GLACIAL MAN IN THE TRENTON GRAVELS? In a paper published in _Science_, Nov. 25. 1892, I undertook to study the evidence relating to paleolithic man in the eastern United States from a new point of view,--that furnished by certain recently acquired knowledge of the contents of quarries and shops where modern aboriginal flaked implements were made. It was shown that all rudely flaked forms could be sufficiently accounted for without the necessity of assuming a very rude state of culture, and that any people, paleolithic or neolithic, would in roughing out blades--the principal product of the flaking process--produce precisely these forms and in great numbers as refuse. It further appeared that the finding of these objects in sporadic cases in glacial gravels or in any formation whatsoever, could not be considered as proving or tending to establish the existence of a particular grade of stone-age culture for the region in which the formation occurs, since they may as readily pertain to a neolithic as to a paleolithic status. It was conclusively shown that no worked stone that can with reasonable safety be called an implement has been reported from the gravels, and that it is therefore clearly useless, not to say unscientific, to go on enlarging upon the evidence of an American paleolithic period and multiplying theoretic details of its culture.